Cara writes about a new drug treatment for ovarian cysts in guinea pigs that her vet found (and I hope will provide additional info when she learns more):

Zipper received a relatively new hormone shot today to reduce the size of her ovarian cyst since I decided surgery wasn't an option I wanted to pursue. It's called gonadotropin-releasing hormome (GnRH) and is different the from usual human chorionic gonadotropin (hcG) used to treat ovarian cyst in guinea pigs.

I've learned the side effects from hcG include an allergic reaction to the subsequent injection site and irritation, edema, and pain. hcG also requires about a 1ml dose which is a large dose for a small pig. It also stimulates an antibody response making the 2nd or 3rd dose potentially less effective.

GnRH, to the knowledge of Jorg Mayer, DMV, doesn't have side effects. According to this vet who apparently has used it the most (at least to the knowledge of my vet) it had reduced the size of the cysts in every case. I don't have any further details but will see what I can dig up to further back this vets claims. My vet has never used it before. It only took two days to order it and wasn't expensive ($23.00 for the shot).

GnRH is typically used in cattle to treat ovarian cysts and inducing estrus in cats. It doesn't stimulate an immune respone.

The dose is 0.5ml for a guinea pig every 2 weeks for 2 injections. The brand name is Cystorelin.

I will try gain further info but the seems like a very promising treatment. Unfortunately, Zipper's cyst is too small to feel and I am not looking to have another ultrasound done in the near future but Dr. Fisher was certain this would reduce the cyst and therefore, hopefully reduce any discomfort thereby reducing her increased respirations and the constant state of bloat she's in. Then again the cyst might not have a thing to do with the bloating.